Rack-and-pinion gear mechanism

ABSTRACT

A rack and pinion gear mechanism includes a rack forming member having a rack; a pinion gear which engages releasably with the rack of rack forming member; and an elastic member which contacts with one portion of the rack forming member and deformed by an elastic deformation corresponding to a displacement of the rack forming member by a confliction of tooth points, the one portion is located opposite side to a tooth of the rack that contacts firstly with a tooth of the pinion gear. The elastic member contacts with the one portion of rack forming member at just before and just after beginning of the engagement between the rack and the pinion gear, and the elastic member is apart from the rack forming member when the engagement is achieved. The rack and pinion gear mechanism further includes a positioning means to fix the elastic member in a cantilever manner to define a positioning of a free end of the elastic member in height. A tooth of the rack which firstly contacts with a tooth of the pinion gear at the engagement with the pinion gear, is made lower than the other teeth in its height of tooth top.

TECHNICAL FIELD

[0001] The present invention relates to a rack and pinion gear mechanismby which an engagement and its releasing can be performed between a rackand a pinion gear.

BACKGROUND ART

[0002] As a rack and pinion gear mechanism in the prior art technology,it is well known, for example, that is disclosed in Japanese Laid OpenPatent Sho 63-176857 patent gazette.

[0003]FIG. 1 is a front view to show a constitution of the rack andpinion gear mechanism in the prior art technology which is disclosed inthe above mentioned Laid Open patent gazette. In the drawing a referencenumeral 1 designates a main body rack, 2 designates a conveying means tocarry pinion series 3A, 3B, 3C and the like. The main body rack 1 isfixed on the main body flame by pins 5 and 6. In a pinion introducingside (which is shown as right side in FIG. 1) of the main body rack 1, aintroducing segment rack 7 is arranged capable of rocking in verticaldirection around a pin 6 as an axis contacting with the main body rack1. At a junction point 8 of an end portion of the main body rack 1 andan end portion 7A of the introducing segment rack 7, a pitch line 11 intooth depth direction of the introducing segment rack 7 and a pitch line13 in tooth depth direction of the main body 1 are matched. And theintroducing segment rack 7 is arranged in relation to the main body rack1 such that a gear pitch 9 of the introducing segment rack 7 at thejunction point 8 is made aligned with a gear pitch 10 of the main bodyrack 1. An end portion 7B of the pinion introducing side of introducingsegment rack 7 is held so that the pitch line 11 in tooth depthdirection becomes at least lower than the pitch line 13 of tooth depthdirection of the main body rack 1 in a predetermined amount 12. At thispoint the above mentioned amount 12 is maintained by means that a block15 which is built as one body in the introducing segment rack 7 ispushed against a stop pin 14 by a boost up force of spring 16.

[0004] And a distance 20 between the stop pin 14 and an end surface ofthe end portion 7B of pinion introducing side of the introducing segmentrack 7 is set less than one half of the gear pitch. The spring 17 is anelastic member to press the introducing segment rack 7 to the main bodyrack 1. A force generated in a tooth surfaces when the introducingsegment rack 7 and the pinion 3B and the like are engaged, can beabsorbed by a displacement and its return in longitudinal direction ofthe introducing segment rack 7.

[0005] Hereinafter operation of the mechanism will be explained.

[0006] When the pinion 3B, for example, usually comes from right handdirection of the drawing and arrives on the introducing segment rack 7,a tooth point of the pinion 3B and a tooth point of the introducingsegment rack 7 interfere together. At this point the introducing segmentrack 7 rocks downward around axis of the pin 6 as a center to absorb theforce generated at the tooth points. By this movement disadvantages suchas a malfunction of the gear mechanism, a damage of driving motor, abreakage of teeth and the like are prevented.

[0007] However in the rack and pinion gear mechanism in the prior arttechnology there has been a problem that a constitution of the gearmechanism is too complicated because a means to prevent thedisadvantages which is generated by a confliction of the tooth points,is composed of the introducing segment rack 7 that moves to a directionto release an engagement when the confliction of tooth points occurs,the spring 16 that always presses the introducing segment rack 7 upwardto hold it at a predetermined position and the spring 17 that urges thegears in a direction for the engagement and makes the gears smoothlyengaged when the engagement is released.

[0008] The present invention has been made to solve the above describedproblem and it is an object of the invention to provide a rack andpinion gear mechanism by which the disadvantages caused by conflictionof the tooth points can be prevented with a simple constitution.

DISCLOSURE OF THE INVENTION

[0009] The rack and pinion gear mechanism in accordance with the presentinvention includes a rack forming member having a rack; a pinion gearwhich engages releasably with the rack of rack forming member; and anelastic member which contacts with one portion of said rack formingmember, which is located opposite side to a tooth of the rack thatcontacts firstly with a tooth of said pinion gear and is deformed by anelastic deformation corresponding to a displacement of the rack formingmember by a confliction of tooth points. By this arrangement an effectis produced that an occurrence of disadvantages such as a damage ofdriving motor, a breakage of teeth and the like caused by theconfliction of tooth points can be avoided, though it has merely asimple constitution in comparison with the gear mechanism in the priorart technology, the elastic member can be deformed by the elasticdeformation corresponding to a displacement of the rack forming memberhaving the rack when the confliction of tooth points occurs at verybeginning of the engagement.

[0010] The rack and pinion gear mechanism in accordance with the presentinvention is arranged such that the elastic member contacts with the oneportion of rack forming member at just before and just after beginningof the engagement between the rack and the pinion gear, and the elasticmember is apart from the rack forming member when the engagement iscontinued. By this arrangement an effect is produced that the rackforming member can be surely reset utilizing an elasticity of theelastic member when it need, and at the same time the contact betweenthe elastic member and the rack forming member can be avoided tosuppress the sliding load as low as possible when it does not need.

[0011] The rack and pinion gear mechanism in accordance with the presentinvention further includes a positioning means to fix the elastic memberin a cantilever manner to define a positioning of free end of theelastic member in height. By this arrangement an effect is produced thata decrease of durability in operation can be avoidable because a heightof the elastic member can be adjusted in order that the elastic memberis slightly contacted with one portion of the rack forming member justbefore and just after beginning of the engagement, and the sliding loadof elastic member against the rack forming member can be suppressed aslow as possible.

[0012] The rack and pinion gear mechanism in accordance with the presentinvention is arranged such that a tooth of the rack which firstlycontacts with a tooth of the pinion gear at the engagement with thepinion gear, is made lower than the other teeth in its height of toothtop. By this arrangement an effect is produced that occurrence of theconfliction of tooth points can be decreased and the smooth engagementcan be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a front view to show a constitution of rack and piniongear mechanism in the prior art technology.

[0014]FIG. 2 is a perspective view to show a rack and pinion gearmechanism in accordance with embodiment 1 of the present invention in astate just before an engagement of tooth points occurs.

[0015]FIG. 3 is a front view of the rack and pinion gear mechanism shownin FIG. 2.

[0016]FIG. 4 is an enlarged perspective view to show a relevant part ofthe rack and pinion gear mechanism shown in FIG. 2.

[0017]FIG. 5 is a perspective view to show the rack and pinion gearmechanism shown in FIG. 2 to FIG. 4 in a state just after an engagementhas been begun without an occurrence of the confliction of tooth points.

[0018]FIG. 6 is a perspective view to show a state that the engagementis proceeded from the state the engagement has been begun as shown inFIG. 5.

[0019]FIG. 7 is a front view to show an action of the rack when it is inthe engagement shown in FIG. 5 and FIG. 6.

[0020]FIG. 8 is a perspective view to show the rack and pinion gearmechanism shown in FIG. 2 to FIG. 4 in a state just after an engagementhas been begun with an occurrence of the confliction of tooth points.

[0021]FIG. 9 is a front view to show an action of the rack when it is ina state of the engagement with the confliction of tooth points.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] For explaining the present invention in more detail, best modefor carrying out the invention will be described hereinafter withreference to the accompanied drawings.

[0023] Embodiment 1

[0024] A rack and pinion gear mechanism in accordance with embodiment 1of the present invention can be applied to, for example, a driving adisk carrying mechanism (not shown in the drawings) which holds acompact disk (hereinafter it is refereed to as “CD”) to carry it to apredetermined position and at the same time evacuates from a projectionsurface of CD when it is in a reproducing state in a CD driving device(not shown in the drawings) by which the reproducing of opticalrecording media such as CD is performed, however, this embodiment 1 isonly an example and the present invention is not limited only to thisembodiment 1.

[0025]FIG. 2 is a perspective view to show a rack and pinion gearmechanism in accordance with embodiment 1 of the present invention in astate just before an engagement of tooth points occurs, and FIG. 3 is afront view of the rack and pinion gear mechanism shown in FIG. 2. FIG. 4is an enlarged perspective view to show a relevant part of the rack andpinion gear mechanism shown in FIG. 2, and FIG. 5 is a perspective viewto show the rack and pinion gear mechanism shown in FIG. 2 to FIG. 4 ina state just after an engagement has been begun without an occurrence ofthe confliction of tooth points. FIG. 6 is a perspective view to show astate that the engagement is proceeded from the state the engagement hasbeen begun as shown in FIG. 5, and FIG. 7 is a front view to show anaction of the rack when it is in the engagement shown in FIG. 5 and FIG.6. FIG. 8 is a perspective view to show the rack and pinion gearmechanism shown in FIG. 2 to FIG. 4 in a state just after an engagementhas been begun with an occurrence of the confliction of tooth points,and FIG. 9 is a front view to show an action of the rack when it is in astate of the engagement with the confliction of tooth points. At thispoint in the drawings an end portion of rack which is nearer to a piniongear is called as a “front end” and an end portion of the rack which isfarther to the pinion gear is called as a “back end” as far as it is notespecially refereed.

[0026] In the drawings a reference numeral 21 designates a rack platewhich has a long plate shape. In an inside front of the rack plate 21 acontinuos length of opening portion 22 is made in a position which isnear to the pinion gear that will be described later. A width of thisopening portion 22 is made wider than an outer diameter of the piniongear (diameter of addendum circle) that will be described later. In aunder edge portion of the opening portion 22 a rack 23 is made which iscomposed of an arrangement of teeth that is disposed along a straightline. In this embodiment 1, the rack is made such that height of a firsttooth 23 a of the rack 23 (tooth height) is lower than the other teethin order to absorb a confliction of tooth points between the rack 23 anda pinion gear that will be described later.

[0027] In the rack plate constituted as described above, a back sideguiding pin 24 and a front side guiding pin 25 which are separated eachother along its long direction, are disposed at a surface opposing to amounting table that will be described later. The back side guiding pin24 is disposed at a back position which is apart from the openingportion 22, and the front side guiding pin 25 is disposed at a frontposition which is near to the opening portion 22. These back sideguiding pin 24 and front side guiding pin 25 are respectively composedof a head portion 24 a and 25 a which have a large outer diameter and afoot portion 24 b and 25 b (not shown) which have a smaller outerdiameter than the head portions.

[0028] Also in a lower front portion of the rack plate 21, a slidingportion 26 is formed, which slides and contacts with an elastic memberthat will be described later. This sliding portion 26 is composed of asliding surface 26 a which receives a sliding by the elastic member thatwill be described later, a front curved surface 26 b which is formed infront of the sliding surface 26 a to absorb a mechanical shock by acontact with the elastic member that will be described later when therack plate 21 moves forward, and a back curved surface 26 c which isformed at the back of the above mentioned sliding surface 26 a to absorbthe mechanical shock by the contact with the elastic member that will bedescribed later when the rack plate 21 moves backward.

[0029] A reference numeral 27 designates the mounting table having along plate shape, and the mounting table is formed on a chassis (notshown) of the above mentioned CD driving device (not shown).

[0030] The mounting table 27 has two guiding grooves which are a backside guiding groove 28 and a front side guiding groove 29 and they areextending along their long direction and separated each other along thesame direction. The back side guiding groove 28 is mainly composed of acircular groove portion 28 a through which head portion 24 a of the backside guiding pin 24 can be inserted, and a straight groove portion 28 bwhich is formed continuously to the circular groove portion 28 a havinga width that is defined within a range between outer diameters of thehead portion 24 a and the foot portion 24 b of the back side guiding pin24.

[0031] Also the front side guiding groove 29 is mainly composed of acircular groove portion 29 a through which head portion 25 a of thefront side guiding pin 25 can be inserted, and a straight groove portion29 b which is formed continuously to the circular groove portion 29 ahaving a width that is defined within a range between outer diameters ofthe head portion 25 a and the foot portion 25 b of the front sideguiding pin 25. In this respect in the straight groove portion 29 bthere is provided a concave portion 30 at a position where the circulargroove portion 29 a is adjoining. The concave portion 30 is composed ofa falling portion 30 a which falls from the straight groove portion 29b, a flat portion 30 b which is formed continuously to a lowest portionof the flat portion 30 a and is parallel to the straight groove portion29 b, and a rising portion 30 c which is formed continuously to the flatportion 30 b and rises to the straight groove portion 29 b. At thispoint a distance between an upper edge portion of the straight grooveportion 29 b and the flat portion 30 b of the concave portion 30 isdefined smaller than the outer diameter of head portion 25 a of thefront side guiding pin 25.

[0032] At a lower edge portion of the mounting table 27, a concaveportion 31 is provided in a vicinity of the above mentioned concaveportion 30 to perform a height adjusting of the elastic member that willbe described later.

[0033] On the mounting table 27 constituted as described above, a piniongear 32 is rotatably fixed to be made enable to engage with the rack 23of rack plate 21. At the same time on the mounting table 27 a drivingmotor 34 to transfer a driving force through a series of idler gears 33to the pinion gear 32.

[0034] Also on the mounting table 27 a leaf spring (elastic member) 35is attached in a cantilever manner. This leaf spring 35 is composed of abase portion 35 b which has a screw hole 35 a for a fixing screw (notshown) to fasten the leaf spring 35 onto the mounting table 27, aprotruding portion 35 c having an inverted V shape which is formed in afree end side that is extending forward from the base portion 35 b, anda engaging portion 35 d which is formed continuously to the protrudingportion 35 c to engage with the concave portion 31 of mounting table 27.The leaf spring 35 is supported at the base portion 35 b by the mountingtable 27 and it is set such that the protruding portion 35 c urges therack plate 21 always upward. However, by means that the engaging portion35 d of the leaf spring 35 is engaged with the concave portion 31 ofmounting table 27, a urging of 21 by the protruding portion 35 c of leafspring 35 is regulated in a level that the rack plate 21 slightlycontacts with the protruding portion 35 c and the rack plate 21 isslidable without any large load, thereby a height of the protrudingportion 35 c is regulated. At the same time because the back sideguiding pin 24 and the front side guiding pin 25 are not pushed torespective upper edge portions of the back side guiding groove 28 andthe front side guiding groove 29, respective large sliding loads to theback side guiding pin 24 and front side guiding pin 25 can be avoided.

[0035] A reference numeral 36 designates a trigger. When at a timingthat, for example, a CD is carried to a reproducing position or to aexchanging position, a command is initiated from a CPU (not shown), thetrigger 36 pushes a back end portion of the rack plate 21 forward toengage the rack 23 and the pinion gear 32, thereby it encourages abeginning of action for a rack and pinion gear mechanism which isconstituted as above described.

[0036] Hereinafter an operation of the mechanism will be explained.

[0037] At first before an operation is initiated, the back side guidingpin 24 and the front side guiding pin 25 of rack plate 21 are supportedin a state that they are inserted into the circular groove portions 28 aand 29 a of back side guiding groove 28 and front side guiding groove29.

[0038] Next as shown in FIG. 2 to FIG. 4, when at a timing, for example,CD is carried to a reproducing position or to a exchanging position, acommand is initiated from the CPU (not shown), the trigger 36 pushesback end portion of the rack plate 21 forward. After the trigger 36pushes the rack plate 21, the driving motor 34 begins a driving by acommand from the CPU (not shown) as well, the driving force istransferred through the series of idler gears 33 to begin a rotation ofthe pinion gear 32. When the rack plate 21 begins to go forward along anarrow X1 direction by the above mentioned pushing of trigger 36, a firsttooth 23 a of the rack 23 and the pinion gear 32 begins to contact. Inthis respect by this embodiment 1 of the present invention because thetooth height of the first tooth 23 a of rack 23 is made lower than otherteeth of the rack 23, the confliction of tooth points can be reduced asmuch as possible thereby a smooth engagement can be realized.

[0039] By this arrangement, the confliction of tooth points is notgenerated usually in this embodiment between the rack 23 and the piniongear 32. In this case respective teeth tops are deeply inserted torespective root of teeth, a smooth engagement is achieved. By thisengagement the rack plate 21 is carried forward along the direction ofarrow X1, and the back side guiding pin 24 and the front side guidingpin 25 are guided along the back side guiding groove 28 and the frontside 29. At just before and just after beginning of the engagement,because the protruding portion 35 c of leaf spring 35 supports the rackplate 21 with sliding and contacting onto the sliding portion 26, thefront side guiding pin 25 can pass over the concave portion 30 of frontside guiding groove 29 and arrives at the straight groove portion 29 b.Because the back side guiding pin 24 arrives directly at the straightgroove portion 28 b from the circular groove portion 28 a, a height ofwhole rack plate 21 is not changed at before and after of the engagementand constant always.

[0040] In this respect a reference symbol A1 in FIG. 7 designates aposture and a position of the rack plate 21 just before the engagementcorresponding to FIG. 2 to FIG. 4, A2 designates a posture and aposition of the rack plate 21 at the engagement corresponding to FIG. 5,and A3 designates a posture and a position of the rack plate 21 justafter the engagement corresponding to FIG. 6.

[0041] If by any possibility the confliction of tooth points occurred,it can be absorbed by means that the leaf spring is deformed by anelastic deformation caused by a force generated by the confliction oftooth points to rotate the rack plate 21 along a direction shown by anarrow Y1 around the back side guiding pin 24 as a center. By thisarrangement malfunction and the like by the confliction of tooth pointsis avoided. Just after the absorption of occurrence of confliction, therack plate 21 in a state of rotation is reset to an original positionalong a direction shown by an arrow Y2 by an elastic reset of the leafspring 35. By this arrangement the respective teeth tops are deeplyinserted to respective root of teeth, thereby the smooth engagement isachieved.

[0042] In a state after the rack plate 21 is reset, the protrudingportion 35 c of leaf spring 35 moves away from sliding portion 26 of therack plate 21, and the back side guiding pin 24 and the front sideguiding pin 25 are guided only by the straight groove portion 28 b ofback side guiding groove 28 and the straight groove portion 29 b offront side guiding groove 29.

[0043] In this respect a reference symbol B1 in FIG. 9 designates aposture and a position of the rack plate 21 just before the conflictionof tooth points occurs, B2 designates a posture and a position of therack plate 21 at the confliction of tooth points corresponding to FIG.8, and B3 designates a posture and a position of the rack plate 21 justafter the confliction of tooth points occurs. A reference symbol C1 inFIG. 9 designates a posture and a position of the leaf spring 35 whenthe rack plate 21 is in a posture and position of B1 and B3, C2designates a posture and a position of the leaf spring 35 when the rackplate 21 is in a posture and position of B2.

[0044] As above described, in any cases when the confliction of toothpoints occurs or does not occur, the driving force by the driving motor34 is transferred to the pinion gear 32 in order to reversely rotate thepinion gear 32 when the rack plate is returned backward along thedirection that arrow X2 shows. By this action the rack plate 21 isreturned backward, thereby the engagement between the rack 23 and thepinion gear 32 is released at the first tooth 23 a of rack 23 sidefinally, then a backward movement of the rack plate 21 is stopped. Asabove described when the rack plate 21 is moved backward, a posture anda height of the rack plate 21 are kept from a beginning of backwardmovement till the pinion gear 32 arrives at the first tooth 23 a of rack23 because the back side guiding pin 24 and the front side guiding pin25 are guided only by the straight groove portion 28 b of the back sideguiding groove 28 and by the straight groove portion 29 b of the frontside guiding groove 29. And at a time point from just before to justafter the pinion gear 32 arrives at the first tooth 23 a of the rack 23,the posture and the height of rack plate 21 are kept because the slidingportion 26 of rack plate 21 is contacted with the protruding portion 35c of leaf spring 35 ant it is supported, only when the front sideguiding pin 25 passes over the concave portion 30 of front guidinggroove 29. Accordingly the posture and the height of rack plate 21 arealways kept when the rack plate 21 moves backward.

[0045] As above described, in accordance with embodiment 1 of thepresent invention because the gear mechanism is constituted such thatthe leaf spring 35 is provided as the elastic member, though it hasmerely a simple constitution in comparison with the gear mechanism inthe prior art technology, the leaf spring 35 can be deformed by theelastic deformation corresponding to a displacement (rotating movement)of the rack plate 21 having the rack 23 when the confliction of toothpoints occurs at very beginning of the engagement between the rack 23and the pinion gear 32, an effect is produced that an occurrence ofdisadvantages such as a damage of driving motor, a breakage of teeth andthe like caused by the confliction of tooth points can be avoided.

[0046] In accordance with embodiment 1 of the present invention aneffect is produced that the rack plate 21 which is shifted with anelastic deformation of the leaf spring 35 in order to absorb theconfliction of tooth points, can be surely reset at the originalposition utilizing an elasticity of the leaf spring 35 because the leafspring 35 is arranged to be apart from the rack plate 21 just before andafter a beginning of the engagement between the rack 23 and the piniongear 32, and at the same time the contact between the leaf spring 35 andthe rack plate 21 can be avoided to suppress the sliding load as low aspossible when the rack 23 and the pinion gear 32 are engaged each other.

[0047] In accordance with embodiment 1 of the present invention a heightof the protruding portion 35 c can be adjusted in order that theprotruding portion 35 c is slightly contacted with the sliding portion26 of rack plate 21 just before and just after beginning of theengagement because it is constituted that the concave portion 31 isformed on the mounting table 27 as a positioning means by which the leafspring 35 is fixed in a cantilever manner and defines a positioning ofthe protruding portion 35 c of free end side of the leaf spring 35 inheight. By this arrangement an effect is produced that a decrease ofdurability in operation can be avoidable because the sliding load ofprotruding portion 35 c against the rack plate 21 can be suppressed aslow as possible.

[0048] In accordance with embodiment 1 of the present invention aneffect is produced that occurrence of the confliction of tooth pointscan be decreased and the smooth engagement can be attained because aheight of the first tooth 23 a of rack 23 is made lower than the otherteeth of the rack 23, which contacts firstly with a tooth of the piniongear 32 when the engagement with the pinion gear 32 is achieved.

INDUSTRIAL APPLICABILITY

[0049] As set forth above, the present invention provides the rack andpinion gear mechanism by which the engagement and its release areachieved between the rack and the pinion gear, and the present inventionis applicable, for example, in a CD driving device for driving of diskconveying mechanism which holds CD to carry to a predetermined position,and at the same time evacuates from a projection surface of CD when itis in a reproducing state.

What is claimed is:
 1. A rack and pinion gear mechanism comprising: arack forming member having a rack; a pinion gear which engagesreleasably with said rack of rack forming member; and an elastic memberwhich contacts with one portion of said rack forming member, which islocated opposite side to a tooth of the rack that contacts firstly witha tooth of said pinion gear and is deformed by an elastic deformationcorresponding to a displacement of the rack forming member by aconfliction of tooth points.
 2. The rack and pinion gear mechanismaccording to claim 1 characterized by that said elastic member contactswith the one portion of rack forming member at just before and justafter beginning of the engagement between the rack and the pinion gear,and the elastic member is apart from the rack forming member when theengagement is continued.
 3. The rack and pinion gear mechanism accordingto claim 2 characterized by further comprising a positioning means tofix the elastic member in a cantilever manner to define a positioning offree end of the elastic member in height.
 4. The rack and pinion gearmechanism according to claim 1 characterized by that a tooth of the rackwhich firstly contacts with a tooth of said pinion gear at theengagement with the pinion gear, is made lower than the other teeth inits height of tooth top.